Nature: Arctic Bears 7 pm
Polar bears are living on borrowed time. They are the descendents of grizzlies, long-ago evolved to live and hunt on the frozen ice of the Arctic, eating a specialized diet of seal meat. But the winters have become increasingly warmer, the ice is disappearing and raising a family becomes a much more difficult proposition when hunting time is short and food is scarce. Grizzlies, on the other hand, are masters at living off the land, making a meal from a wide variety of foods — meats, seeds, berries, insects, fruit and honey. Their world is bountiful and expanding northward, converging with what once was the icy domain of the polar bear. As the two worlds meet, are the polar bears fated to become grizzlies once again?

NOVA: Extreme Ice 8 pm
In collaboration with National Geographic, NOVA follows the exploits of acclaimed photojournalist James Balog and a scientific team as they deploy time-lapse cameras in risky, remote locations in the Arctic, Alaska, and the Alps. Grappling with blizzards, fickle technology, and climbs up craggy precipices, the team must anchor cameras capable of withstanding sub-zero temperatures and winds up to 170 mph. The goal of Balog’s team’s perilous expedition: to create a unique photo archive of melting glaciers that could provide a key to understanding their runaway behavior and their potential to drive rising sea levels. Some models now project a one-meter sea level rise over the next century, which could displace millions of people everywhere from Florida to Bangladesh and require trillions of dollars in new coastal infrastructure investments. But, alarmingly, these models don’t reflect recent findings that glaciers in Greenland and Antarctica are melting at an ever-faster rate. What explains this alarming acceleration, and just how do you figure out what’s happening inside a gigantic wall of ice? In this high-action scientific adventure, NOVA investigates the mystery of the mighty ice sheets that will affect the fate of coastlines around the world.

NOVA: Secrets Beneath The Ice 9 pm
In 2002, an immense, 200 meter-thick ice shelf, the size of Manhattan, collapsed into the ocean off the Antarctic Peninsula, shocking scientists and raising the alarming possibility that we may be heading toward an ice-free Antarctica — last seen a million years ago. That would raise world sea levels so high that New York City would be flooded up to the level of the Statue of Liberty’s shoulders. But could this really happen? Is Antarctica’s surprising past a reliable guide to what may happen to our warming planet? To gather crucial evidence, NOVA follows the most ambitious scientific project launched during the International Polar Year: a state-of-the-art drilling probe known as ANDRILL. Penetrating more than a kilometer through the floating sea ice, ANDRILL recovers evidence from the seabed that reveals details of climate and fauna from a time when dinosaurs and forests once thrived in Antarctica. As the scientists grapple with the harshest conditions on earth, they discover astonishing and disturbing new clues. Once thought to be locked in a solid deep freeze for the last 15 million years, it now looks like Antarctica’s ice has melted and frozen again dozens of times during that period. This breakthrough discovery carries ominous implications for coastal cities around the globe.